The South St. Paul man accused of fatally shooting National Guard Staff Sgt. Brandon Horst in the head has 20 personalities and other mental illness, said his attorney.

Aaron W. Allen, 25, should undergo a psychiatric evaluation to determine his mental competency, his attorney, Mike Carsten, said in Ramsey County District Court Tuesday.

Allen has dissociative identity order, also referred to as multiple personality disorder, is bipolar and suffers from post-traumatic stress disorder, Carsten told District Court Judge John Guthmann.

The PTSD stems from sexual and emotional abuse Allen suffered as a child, Carsten said, adding that Allen’s mental health issues have been diagnosed in the last 15 years.

“I have noticed, as have my staff, some manifestation of mental illness so that sometimes I don’t know who I’m talking to,” Carsten said.

Allen is charged with aiding and abetting second-degree murder and conspiracy to commit second-degree murder. Carsten said Allen doesn’t understand the charges against him.

According to charges: Horst’s wife, Heather L. Horst, 24, told Allen and others that she was unhappy in her marriage and that her husband allegedly abused her.

Horst allegedly told Allen, “I want him dead,” and that she wanted the shooting to look like a break-in, according to charges. She picked Allen up around 10:30 p.m. Aug. 4 and went to the couple’s St. Paul home. She left her gun inside for Allen to use. He waited in the basement for Brandon Horst, 25, to fall asleep before shooting him, charges said.

Horst called 911 shortly after 1 a.m. on Aug. 5 to report the shooting. She’s also charged with aiding and abetting second-degree murder and conspiracy to commit second-degree murder.

Allen will be evaluated to assess his mental state at the time of the shooting and his ability to understand the current court proceedings. The results are expected to be presented at a Dec. 10 hearing.

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